High intensity magnetic sorter

ABSTRACT

A high intensity magnetic sorter in which a mixture of feebly magnetic particles and non-magnetic particles are fed to the top portion of a rotary wheel rotable about a horizontal axis and influenced by an intense magnetic field creating field gradients increasing radially toward the wheel for attracting the magnetic particles toward the wheel, and deflector plates for guiding the separated non-magnetic particles and magnetic particles from the rotating wheel to separate deposit stations.

United States Patent 1191 Lee et al.

1 HIGH INTENSITY MAGNETIC SORTER [75] Inventors: Jeh-Mann Lee; Charles E. Roos,

both of Nashville, Tenn.

[73] Assignee: Vanderbilt University, Nashville,

Tenn.

1221 Filed: Aug. 31, 1973 1211 Appl. No.: 393.662

[ 1 Nov. 25, 1975 3,375,925 4/1968 Carpenter 209/214 3,627,678 12/1971 Myrston 210/42 FOREIGN PATENTS OR APPLICATIONS 637,992 3/1935 Germany 209/219 744,169 11/1943 Germany 209/223 Primary ExaminerRobert Halper Attorney, Agent, or FirmHarrington A. Lackey ABSTRACT 209/223 A high intensity magnetic sorter in which a mixture of [58] Field of Search 209/223, 219, 214, 232, s f f 209,213 230 228 are e to t e top po rt1on o a rotary w ee rota e about a honzontal ax1s and mfluenced by an 1ntense magnetic field creating field gradients increasing radi- [56] References Cited ally toward the wheel for attracting the magnetic par- UNITED STATES PATENTS ticles toward the wheel, and deflector plates for guid- 464,816 12/1891 Cunkling 209/219 ing the separated non-magnetic particles and magnetic 5551792 3/1396 Wetherillm 209/2l4 X particles from the rotating wheel to separate deposit 676,841 6/1901 Edison 209/219 x Stations 2,841,285 7/1958 Box 209/223 R 3,057,477 10/1962 Rappaport 209/223 R 2 Claims, 5 Drawing Figures US. Patent N0v.-25, 1975 HIGH INTENSITY MAGNETIC SORTER BACKGROUND OF THE INVENTION This invention relates to a magnetic sorter, and more particularly to a high'intensity magnetic sorter for feebly magnetic materials and non-magnetic materials.

It is known in the art to provide a pulley having bar magnets in the periphery thereof for attracting magnetic materials carried by an endless belt around the pulley, so that magnetic particles are separated from non-magnetic particles fed around the pulley. The nonmagnetic particles drop from the pulley by gravity, while the magnetic particles are held by magnetism against the pulley until they are diverted away from the magnetic influence of the pulley.

Such prior art magnetic pulleys produce low-order fields of magnetism, which are more than adequate for separating ferromagnetic particles, such as iron, cobalt or nickel, from non-magnetic particles. However, such fields created by simple bar magnets are totally inadequate for separating feebly or weakly magnetic particles from non-magnetic particles. The magnetic fields created by the bar magnet not only move with the pulley, but also produce non-uniform fields circumferentially of the pulley. The magnetic forces of greatest strength are concentrated at the intermittently spaced bar magnets to attract magnetic particles in bunches to the rim of the conventional magnetic pulleys.

SUMMARY OF THE INVENTION It is therefore an object of this invention to provide a rotary sorter wheel or pulley, at least a portion of the outer rim of which is under the influence of an intense stationary magnetic field, circumferentially uniform around the wheel, and having high field gradients for producing strong magnetic forces radially toward the wheel. Feebly magnetic particles fed to the periphery of the wheel are thus magnetically attracted to the wheel, while non-magnetic particles drop from the wheel by gravity.

This intense magnetic field is created by stationary electromagnets larger than conventional electromagnets and energized by currents of high amperage. The iron cores of the large electromagnet are spaced on opposite sides of the wheel and are provided with specially shaped pole tips, which not only transmit the high intensity magnetic field, but also produce magnetic field gradients of high values increasing radially inward toward the wheel so that the most intense part of the field is closely adjacent to the outer rim of the wheel. The resultant, radially inward, magnetic forces are thus strong enough to attract the feebly magnetic particles against the rim of the rotating wheel.

As the particles are carried around the rim of the wheel from a feeding position on top of the wheel, the non-magnetic particles are thrown off the wheel by centrifugal force and drop by gravity through an appropriate chute to a deposit station. The magnetic particles, being attracted to the rim of the wheel are carried around toward the bottom of the wheel. The magnetic particles are physically separated from the rim of the wheel by a deflector plate, and preferably by an endless belt trained around the wheel and over the deflector plate, to remove the magnetized particles from the influence of the magnetic field and magnetic field gradients. When the gravitational force and the centrifugal force exceed the magnetic attractive force, the feebly 2 magnetic particles also drop by gravity to a second deposit station substantially spaced from the first deposit station of the non-magnetic particles.

By virtue of the strength of the magnetic field and field gradients, particles may be fed more rapidly to the wheel, such as by the endless belt, to produce a more rapid separation rate, and thereby improve production.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional elevation of the sorter made in accordance with this invention, taken along the line 1-1 of FIG. 2;

FIG. 2 is a fragmentary top plan view of the portion of the sorter including the sorter wheel and magnet, with portions broken away;

FIG. 3 is a slightly enlarged section taken along the line 3-3 of FIG. 1, with the deflector plates removed;

FIG. 4 is an enlarged fragmentary section taken along the line 44 of FIG. 1; and

FIG. 5 is an enlarged section taken along the line 5--5 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in more detail, FIG. 1 discloses the paramagnetic sorting apparatus 10, including a sorter frame 11 and a conveyer frame 12, both of which are stationary, and which may be connected to each other.

Mounted upon the sorter frame 11 is a large C- shaped electromagnet 14 having a C-shaped-Qtir inverted U-shaped, flux return piece 15 made from highly permeable magnetic material, preferably iron. Fixed to,

or forming an integral part of, the opposed inner surfaces of the legs of the return piece 15 are a pair of cylindrical iron cores l6 and 17, having respective pole tips 18 and 19, terminating in opposed pole faces defining an air gap. Surrounding the cores 16 and 17 are coils 20 and 21 of electrical conductors, supplied with current of high amperage through power supply leads 22, from any convenient source of high voltage electricity, not shown.

Mounted for rotary movement upon a shaft 24, preferably co-axially of the cylindrical cores 16 and 17 and within the air gap between the-pole tips 18 and 19, is a sorter wheel or head pulley 25, made of non-magnetic material. Trained aroundthe head pulley 25 is an endless belt 26 of uniform width substantially equal to the width of the head pulley 25 and also substantially spanning the air gap between the pole tips 18 and 19. The endless belt 26 is also trained about the driven tail pulley 28 rotatably mounted upon driven shaft 29 at the rear end of the conveyor frame 12. Shaft 29 is driven through the sprocket and chain transmission 30 from a variable speed motor 31, for moving the endless belt 26 in the direction of the arrow disclosed in FIG. 1.

Supported upon the conveyor frame 12 is a channelshaped trough 33, having the configuration, best disclosed in FIG. 4. The trough 33 has a flat bottom wall 34 of substantially the same width as the endless belt 26, to support belt 26 as it moves over the top surface of the bottom wall 34. The bottom portions 35 of the side walls diverge upward and terminate in the straight vertical upper side wall portions 36. The bottom wall 34 extends forward to terminate in a front edge 37 closely adjacent to the surface of the head pulley 25, to permit the endless belt 26 to feed tangentially over the outer rim of the head pulley 25. Trough 33 is disclosed 3 as being horizontal, but of course may decline toward the head pulley 25 at other angles, if desired.

Mounted above the rear portion of the trough 33, by means not shown, is a hopper 39 having a discharge spout 40, for discharging a mixture of feebly magnetic particles 41 and non-magnetic particles 42 upon the conveyor belt 26.

The return leg of the endless belt 26 is trained about the idler pulleys 44, 45 and 46, so that the belt 26 makes an almost 180 degree wrap about the head pulley 25, and is provided with a greater than 180 degree wrap about the tail pulley 28.

A portion of the return leg of the endless belt 26 between the bottom of the head pulley 25 and idler pulley 44 is supported by an inverted return trough 48 fixed upon the sorter frame 11. As is best disclosed in FIG. 5, the return trough 48 has a channel-shape similar to the feed trough 33. The top wall 49 of the return trough 48 terminates in an edge 50 spaced quite close to the rim of the head pulley 25 to provide a substantially straight support for the return portion of the endless belt 26, particularly while the magnetic particles are still under the influence of the magnetic field around the head pulley 25.

A deflector plate 53 is mounted on the frame 11 below the return trough 48 in such a manner that it may form with the return trough 48 a discharge chute for the magnetic material 41.

Another deflector plate 54 is mounted upon the sorter frame 11 for directing the non-magnetic particles 42, dropping by gravity from the belt 26, to a deposit station (not shown) spaced from the deposit station for the magnetic material 41. The deflector plate 54 may form one wall of a discharge chute 55.

The deflector plates 53 and 54 may be supported in any desired manner upon the sorter frame 11, but are preferably so mounted that they may be shifted to dif ferent positions for catching and diverting the respective streams of magnetic particles 41 and non-magnetic particles 42. As disclosed in FIG. 1, the diverter plates 53 and 54 are connected to each other by a piano hinge 57 for pivotal movement relative to each other and to the frame 11. Plate 53 may also be provided with bolts 58 for limited movement in slots 59, while the plate 54 may be provided with a bolt 60 for limited movement in the corresponding slot 61.

Ring-shaped shields 63 are mounted against the inner surfaces of the coils 20 and 21 to protect them from the particles fed by the endless belt 26 to the sorter wheel 25 and also to prevent the accumulation of dirt and dust upon the coils 20 and 21.

In the construction of the sorter apparatus 10, the return flux piece 15, cores 16 and 17 and their respective pole tips 18 and 19 are made of solid iron. The sorter frame 11 is preferably made of steel for strength, and may also provide an alternate flux path for the cores 16 and 17.

The head pulley 25, troughs 33 and 48, deflector plates 53 and 54, and discharge chute 55, are preferably made of non-magnetic metals, such as stainless steel. The coil shields 63 are preferably made of nonmagnetic metal, such as aluminum.

The structure and location of pole tips 18 and 19 are extremely important to the successful function of this invention. As disclosed in the drawings, the pole tips 18 and 19 have frusto-conical shapes and are mirror images of each other. The inner surface of each pole tip 18 and 19 is circular and substantially equal to the di- 4 ameter of the sorter wheel 25, or to the sum of the diameter of the sorter wheel 25 and twice the thickness of the endless conveyor belt 26.

As best disclosed in FIG. 3, the magnetic field lines 65 form an arcuate pattern between the adjacent upwardly diverging frusto-conical surfaces of the pole tips 18 and 19 and uniformly around the pulley 25. Accordingly, there is the greatest concentration of magnetic field lines closest to the belt 26 engaging the rim of the pulley 25. Proceeding radially outward from the sorter wheel 25, the field lines 65 become less and less concentrated, that is, farther and farther apart, so that magnetic field gradients result which increase in value radially toward the wheel 25. Thus, magnetic forces, illustrated by the force lines 66 in FIG. 3, are produced normal to the field lines 65, so that there is a strong magnetic force generally radially inward toward the wheel 25. Because of the arcuate pattern of the field lines 65, the lines of force toward the edges of the wheel 25 are directly laterally inward. The greater the magnitude of the field gradients, the greater strength of the magnetic forces.

If the diameter of the sorter wheel 25 is less than the diameter of the parallel inner faces of the pole tips 18 and 19, no significant gradients exist between the parallel face surfaces of the pole tips 18 and 19 because the magnetic field is of nearly equal concentration and therefore there is almost no change in the magnetic field in this area. Accordingly, the greatest magnetic forces produced by the gradients between the converging surfaces of the pole tips 18 and 19 would be substantially above the belt 26. Such an arrangement would constitute an inefficient utilization of the magnetic field gradients for the separation of the feebly magnetic particles 41.

If the diameter of the wheel 25 were greater than the diameter of the inner pole faces, then the greatest value of the magnetic gradients and the resultant magnetic forces would be created somewhere in the body of the pulley or wheel 25 radially inward from the belt 26, which would not only waste magnetic energy, but would create weaker magnetic forces than those in the pole and wheel arrangement of FIG. 3, all the current and magnetic values otherwise being equal.

In the actual commercial operation of the sorter apparatus 10, weakly magnetic particles 41 in the form of ferro-phosphorus particles have been separated from non-magnetic slag. In this commercial apparatus, a maximum magnetic field of 15 kilogauss was created producing field gradients of approximately I kilogauss per centimeter (2.54 kilogauss per inch). Feebly magnetic particles of ferro-phosphorous from small fines up to particles approximately 4 inch in diameter were readily separated. Moreover, it was immaterial whether the magnetic and non-magnetic particles were wet or dry. The width of the belt 26 in the commercial apparatus 10 is 3% inches and the linear velocity of the belt was approximately 3 to 5 feet per second. Under such conditions, separated products have been obtained as pure as 98-99%.

More intense apparatus 10 may be used in which the magnet 14 develops fields as high as 30 kilogauss, gradients of l-2 kilogauss per centimeter, and utilizing belt speeds of 8 feet per second.

With such a high intensity magnetic field and such strong magnetic field gradients, the speed of the belt may be greater than when it is moving through a much smaller magnetic field, with weaker field gradients, to

increase the production of separating non-magnetic and magnetic materials. The location of thedeflector plates 53 and 54 is adjusted according to the strength of the magnetic field across the sorter wheel 25 andalso depending upon the linear speed of the belt 26. The location of the deflector plate 54 also may depend .upon the size of the non-magnetic particles 42, as well as the speed of the belt 26. V i

In the operation of the apparatus 10, the mixture of magnetic particles 41 and non-magnetic particles 42 are fed from the hopper 39 down through the discharge chute 40 upon the forwardly moving conveyor belt 26.

As the particles approach the rotating sorter wheel 25' they come under the influence of the magnetic field, first passing through the weak field gradients and then gradually through the stronger field gradients, as that portion of the belt 26 supporting the particles engages the rapidly rotating sorter wheel 25. As the belt 26"continues around the wheel 25, the non-magnetic particles 42 are thrownoff by centrifugal force in a parabolic trajectory and dropped by gravity, as illustrated in FIG. 1, into the first discharge chute 55, where the non-magnetic particles 42 are dropped to any convenient deposit station or receptacle, not shown.

On the other hand, the magnetic particles 41, under the influence of the high intensity magnetic field 65, are held upon the moving belt 26 with a circumferentially uniform magnetic attractive force, as the belt moves around the forward portion of, and toward the bottom of, the wheel 25. Because of the circumferential uniformity of the field gradients, the magnetic field may remain stationary while the sorter wheel 25 and belt 26 rotate.

Because of the strong magnetic forces acting upon the feebly magnetic particles 41, the wall 49 of the trough 48 becomes mandatory to prevent this portion of the belt 26 from sagging upward. After the belt 26 passes the front edge 50 of the top plate 49 and continues to move along the plate 49, the magnetic particles 41 are gradually removed from the influence of the magnetic field until they reach a point where the force of gravity is greater than the magnetic attraction, and the particles 41 drop upon the deflector plate 53 and are carried by gravity to a second deposit station, such as a receptacle or another conveyor, not shown. The belt 26, after discharging all of the particles, passes sequentially around the idler pulleys 44, pulleys 45 and 46, and around the tail pulley 28, to receive another charge of particles 41 and 42 from the discharge chute 40.

The magnetic fields and magnetic field gradients generated by the C-shaped magnet 14 are each approximately times the fields and gradients employed in conventional magnetic pulleys. For the reasons previously discussed, the belt speed is also much faster than belt speeds for conventional magnetic pulley separaters.

The C-shaped magnetic flux piece 15 is made of solid iron and has a uniform width as illustrated in FIGS. 1,

and 2, to provide a continuous flux return path. The C- shaped magnetic flux return piece 15 also has an advantage over an entirely closed return flux piece, such as a hollow housing or drum configuration, since the I The particular channel-shaped trough 33 is designed to conform .to the cross sectional shape of the particle feed path around the head pulley and between the frusto-conical surfaces of the pole tips 18 and 19 and the coil shields 63, revealed in FIG. 3. Thus the trough and pole tips provide continuity of shape for feeding the particles from the trough 33 upon the sorter wheel 25. The shape of the trough 33 is also designed to minimize clogging ,of the belt 26. If the side walls of the trough 33 were vertical so that the trough had an exact U-shape, all the material deposited in the trough would bear down upon the belt 26. However, the particular channel configuration, illustrated in FIG. 4, of the trough 33 permits the belt 26 to directly suppo t only a portion of the material deposited in the trough. The portions of material along the sides of the trough are supported by the declining walls 35, which also assist in feeding particles from the sides of the trough 33 down upon the belt 26 as the belt 26 progresses through the trough 33.

As illustrated in FIG. 3, all of the magnetic force lines 66 tend to force the magnetic particles 41 toward the center of the belt 26, thus tending to keep most of the magnetic particles away from the pole tips 18 and 19 for more efficient movement of the magnetic particles, and also to minimize wear of the magnetic particles against the pole tips 18 and 19. Furthermore, the magnetic forcing of the particles to the center of the belt 26 also minimizes the chances of magnetic particles jamming between the belt 26 and the pole faces 18 and 19. Sealed spacer elements, not shown, may be fitted between the pole tip faces and the pulley 25 to minimize particles falling into the air gap and jamming the head pulley 25.

The angle which the frusto-conical surfaces of the pole tips 18 and 19 makes with the flat pole tip face, or the direction of particle feeding, is preferably 3060 for relatively large size magnetic particles 41, as opposed to finely divided particles, such as powder or fines. The angle the frusto-conical pole tip surfaces disclosed in FIG. 3 is 45. This angle is determined by the general size of the input particles, and particularly the size of the magnetic material 41. For very small size magnetic particles 41, such as tines, truncated pole tips are not needed. Cylindrical pole tips would suffice, provided the diameter of the opposed pole faces are substantially equal to the diameter of the sorter wheel 25. Furthermore, the feed trough 33 might have a pure U- shaped channel cross section.

Since there are no particles traveling around the back side of the head pulley 25, that is between the wall edges 37 and 50, no magnetic field is needed in this area. Hence, the magnet cores 1'6 and 17 and the pole tips 18 and 19 do not have to be completely cylindrical, but may be segments of cylinders opposing each other only along the path of the particles 41 and 42 around the head pulley 25.

What is claimed is:

1. A high intensity magnetic sorting apparatus for the separation of feebly magnetic materials from non-magnetic materials comprising:

a. a sorter wheel having a circumferential rim portion of uniform width,

b. a frame supporting said wheel for rotary movement about a horizontal axis and said rim portion for movement in an operative feed path for said magnetic materials,

c. drive means rotating said wheel,

d. an electromagnet stationarily mounted on said frame, and having pole tips spaced on opposite sides of said wheel,

e. said pole tips having inner faces spaced apart on opposite sides of said rim portion a distance slightly greater than the width of said rim portion,

f. each of said pole faces comprising at least a circular segment coaxial of said wheel, having a diameter substantially equal to the diameter of said wheel, and extending circumferentially parallel to, and at least the length of, said operative feed path,

g. said pole tips being shaped to create a magnetic field, when said electromagnet is energized, across said rim portion to produce magnetic field gradients increasing radially inward toward the exterior periphery of said rim portion, and to produce maximum field gradients immediately adjacent the exterior periphery of said rim portion,

h. endless belt means carried circumferentially around said sorter wheel coinciding with said operative feed path for feeding a mixture of feebly magnetic particles and non-magnetic particles in a path toward said wheel and substantially tangent to said v 8 rim portion, so that said particles are carried around said rim portion within said magnetic field and said feebly magnetic particles are magnetically attractedtoward the exterior periphery of said rim portion by the magnetic force produced by said increasing gradients, so that said feebly magnetic particles move along said operative feed path around said wheel rim portion, i. means for energizing said electromagnet,

j. means for receiving the non-magnetic material pole tip surfaces are at least the segments of the frustum of a cone converging toward said inner pole faces. 

1. A HIGH INTENSITY MAGNETIC SORTING APPARATUS FOR THE SEPARATION OF FEEBLY MAGNETIC MATERIALS FROM NON-MAGNETIC MATERIALS COMPRISING: A. A SORTER WHEEL HAVING A CIRCUMFERENTIAL RIM PORTION OF UNIFORM WIDTH, B. A FRAME SUPPORTING SAID WHEEL FOR ROTARY MOVEMENT ABOUT A HORIZONTAL AXIS AND SAID RIM PORTION FOR MOVEMENT IN AN OPERATIVE FEED PATH FOR SAID MAGNETIC MATERIALS, C. DRIVE MEANS ROTATING SAID WHEEL, D. AN ELECTROMAGNET STATIONARY MOUNTED ON SAID FRAME, AND HAVING POLE TIPS SPACED ON OPPOSITE SIDES OF SAID WHEEL, E. SAID POLE TIPS HAVING INNER FACES SPACED APART AN OPPOSITE SIDES OF SAID RIM PORTION A DISTANCE SLIGHTLY GREATER THAN THE WIDTH OF SID RIM PORTION, F. EACH OF SAID POLE FACES COMPRISING AT LEAST A CIRCULAR SEGMENT COAXIAL OF SAID WHEEL, HAVING A DIAMETER SUBSTANTIALLY EQUAL TO THE DIAMTER OF SAID WHEEL, AND EXTENDING CIRCUMFERENTIAL PARALLEL TO, AND AT LEAST THE LENGTH OF, SAID OPERATIVE FEED PATH, G. SAID POLE TIPS BEING SHAPED TO CREATE A MAGNETIC FIELD, WHEN SAID ELECTROMAGNET IS ENERGIZED ACROSS SAID RIM PORTION TO PRODUCE MAGNETIC FIELD GRADIENTS INCREASING RADIALLY INWARD TOWARD THE EXTERIOR PERIPHERY OF SAID RIM PORTION, AND TO PRODUCE MAXIMUM FIELD GRADIENTS IMMEDIATELY ADJACENT THE EXTERIOR PERIPHERY OF SAID RIM PORTION, H. ENDLESS BELT MEANS CARRIED CIRCUMFERENTIALLY AROUND SAID SORTER WHEEL COINCIDING WITH SAID OPERATIVE FEED PATH FOR
 2. The invention according to claim 1 in which the pole tip surfaces are at least the segments of the frustum of a cone convErging toward said inner pole faces. 